Directional optics for a system for directing a laser beam toward an active area

Abstract

A device and method for aligning the focal point of a laser beam into coincidence with the active area of a detector includes an optical element for focusing the laser beam to the focal point at a location on the surface of the detector. Also included is a selectively activated light source and a camera which establishes a reference location for the active area within an x-y grid coordinate system whenever the surface of the detector is illuminated by the light source. Further, by using the light that is reflected from the focal point location through a beam splitter, the camera also establishes the location of the laser beam focal point in the same coordinate system. The optical element is then adjusted to move the focal point in the x and y directions, as required, to thereby bring the focal point location into coincidence with the active area. When an optical system, such as a reflector telescope, is used to establish a partially obscured in-coming beam, a lens and prism can be positioned in the obscuration to collect and focus light scattered from the focal point at the detector and direct it toward the camera for alignment purposes.

What is claimed is: 
     
       1. A device for aligning a light beam with a detector which comprises: means for defining a beam of light, the beam having an optical axis and a cross section in a plane perpendicular to the axis, the cross section having a hole therein for at least a portion of the beam;   means for focusing the beam to a spot on said detector;   means for collecting light scattered into the hole of the beam from the spot on the detector;   means for directing the collected light off-axis; and   a camera positioned at a distance from the axis of the beam for receiving the off-axis light from said directing means to determine a location for the spot on said detector.   
     
     
       2. A device as recited in claim 1 further comprising: a grid oriented on said detector for determining the location of the spot relative to said grid; and   means for adjusting said focusing means relative to said detector to maintain the spot at a predetermined location on said grid.   
     
     
       3. A device as recited in claim 1 further comprising an interference filter positioned between said generating means and said detector for confining the beam of collimated light to a band of wavelengths. 
     
     
       4. A device as recited in claim 3 wherein said band is a range of wavelengths between approximately 775 nm and 795 nm (785 nm±10 nm). 
     
     
       5. A device as recited in claim 3 wherein said directing means is mounted on said interference filter. 
     
     
       6. A device as recited in claim 1 wherein said focusing means is a first lens. 
     
     
       7. A device as recited in claim 6 wherein said collecting means is said first lens. 
     
     
       8. A device as recited in claim 1 wherein said directing means includes a prism to establish an off-axis path for the collected light. 
     
     
       9. A device as recited in claim 8 wherein said directing means further includes a second lens for focusing the collected light along the path and onto said camera. 
     
     
       10. A device as recited in claim 9 wherein the path of the collected light is substantially perpendicular to the axis of the laser beam. 
     
     
       11. A device as recited in claim 1 wherein said generating means is a telescope. 
     
     
       12. A method for aligning a light beam with a detector in a device which comprises the steps of: defining a beam of light, the beam having an optical axis and a cross section in a plane perpendicular to the axis, the cross section having a hole for at least a portion of the beam;   focusing the beam with a focusing means to a spot on the detector;   collecting light scattered into the hole of the beam from the spot on the detector;   directing the collected light off-axis; and   receiving the off-axis light to determine a location for the spot on the detector.   
     
     
       13. A method as recited in claim 12 further comprising the steps of: orienting a grid on the detector for determining the location of the spot relative to the grid; and   adjusting the focusing means relative to the detector to maintain the spot at a predetermined location on the grid.   
     
     
       14. A method as recited in claim 13 further comprising the step of fixing the focusing means relative to the detector to maintain an internal alignment of the laser beam with the detector. 
     
     
       15. A method as recited in claim 14 further comprising the step of moving the device relative to the laser beam to maintain an external alignment of the laser beam with the detector. 
     
     
       16. A method as recited in claim 12 further comprising the step of positioning an interference filter on the axis of the beam to confine the beam of light to a band of wavelengths. 
     
     
       17. A method as recited in claim 16 wherein said band is a range of wavelengths between approximately 775 nm and 795 nm (785 nm±10 nm). 
     
     
       18. A method as recited in claim 12 wherein the light beam is collimated laser light. 
     
     
       19. A method as recited in claim 18 wherein the cross section of the beam surrounding the hole is formed as an annulus.